In conventional semiconductor manufacturing processes, ion implantation into a substrate is typically performed through a thermal oxide layer. During ion implantation, oxygen atoms are likely to be driven into the silicon lattice of the substrate. This phenomenon, known in the industry as oxygen “knock on”, is responsible for current leakage into the substrate that may degrade operation. Thus, knock-on oxide provides a source for crystalline defects. To offset the effects of knock-on oxide, adequate thermal annealing with its inherent diffusion of impurities is typically performed to contain the defects within the dopant profile.
Ion implantation also introduces substrate crystal damage, in which lattice atoms are knocked out of lattice sites, while at the same time a certain number of the newly-introduced atoms will likewise come to rest in positions outside the lattice positions. Such out-of-position phenomena are termed defects. A vacant lattice site is termed a vacancy defect, while an atom located at a non-lattice site is referred to as an interstitial defect. Another defect is the creation of amorphous silicon which must be annealed to return it to its crystalline state. The restorative method generally employed in the art consists of annealing the substrate, where heat is applied to the lattice to mildly energize the atoms, allowing them to work themselves back into the lattice structure and restoring the ion-implanted substrate to its pre-implant condition.